Effects of PM2.5 and its constituents on hemoglobin during the third trimester in pregnant women

Anemia has been a public health issue evoking global concern, and the low hemoglobin (Hb) concentration links to adverse pregnancy outcomes. However, the associations of PM₂.₅ and its constituents with Hb and anemia in pregnant women remain unclear. In this retrospective birth cohort study, 7932 pregnant women who delivered in the First Affiliated Hospital of Xi’an Jiaotong University from 2015 to 2018 were included. The Hb during the third trimester in pregnant women was assessed before delivery. PM₂.₅ and its constituents (BC, NH₄⁺, NO₃⁻, OM, SO₄²⁻, and Dust) during pregnancy were retrieved from the V4.CH.03 product constructed by the Atmospheric Composition Analysis Group. Generalized linear regression model was applied to investigate the effects of PM₂.₅ and its constituents on Hb and anemia during the third trimester in pregnant women. The means and standard deviations of PM₂.₅, BC, NH₄⁺, NO₃⁻, OM, SO₄²⁻, and Dust were 69.56 (15.24), 10.02 (2.72), 8.11 (1.77), 14.96 (5.42), 15.36 (4.11), 10.08 (1.20), and 10.98 (1.85) μg/m³, respectively. Per IQR increase (μg/m³) of PM₂.₅, BC, NO₃⁻, and OM linked to − 0.75 (− 1.50, − 0.01), − 0.85 (− 1.65, − 0.04), − 0.79 (− 1.56, − 0.03), and − 0.73 (− 1.44, − 0.03) g/L decrease of Hb during the third trimester in multiparous pregnant women, but not for NH₄⁺, SO₄²⁻, Dust, and primiparous pregnant women. PM₂.₅ and its constituents had no significant association with anemia, except for Dust (OR: 0.90, 95% CI: 0.82, 0.99, per IQR increase) in primiparous pregnant women. Besides, SO4²⁻ was of lag effects on Hb and anemia in multiparous pregnant women. Moreover, non-linear associations were found among PM₂.₅ and its constituents, Hb, and anemia. Therefore, exposure to PM₂.₅ and some constituents of PM₂.₅ was associated with reduced Hb level during the third trimester in multiparous pregnant women. Related departments and pregnant women should take targeted actions to eliminate the detrimental effects of PM₂.₅ and its constituents on pregnancy outcomes.